This invention relates primarily to the field of telephone equipment, and more particularly to an improved line status indicator device showing the condition of one or more telephone lines to a potential caller without the necessity of actually dialing a desired number. Devices of this type are generally known in the art, and are principally for inter-office communications where particular extensions are dialed directly without the necessity of going through a switchboard. The devices may also be used by a switchboard operator, where desired. Prior art devices include a case containing a plurality of light-emitting diodes, one for each sensed telephone line. Where the phone is in use, the light-emitting diode glows continuously indicating that the receiver is off the hook. Where the line is either receiving a ring current or transmitting a dial pulse, the normal 90-volt ringing current will cause the light-emitting diode to blink at a frequency corresponding to the ringing current. In prior art devices, the light-emitting diode is protected from direct communication with the ringing voltage by so-called opto-isolators which include a light generating source, and a photosensitive element passing a current corresponding to the intensity of light received. These devices are quite expensive, and have added substantially to the total cost of manufacture of the prior art devices.